The invention relates to methods of and apparatus for identifying an eye disorder of an observer. More specifically, the invention relates to identifying an eye disorder, such as amblyopia and myopia, by performing multiple contrast sensitivity function procedures and comparing the results of the procedures.
Early detection can be critical for successful treatment of amblyopia (“lazy eye”), the most common cause of monocular visual impairment in children and young adults that affects 2-5% of the population. Earlier detection of the disorder and correction of the underlying cause (strabismus, refractive error, and/or form deprivation) can provide better long-term treatment outcomes.
A typical amblyopia screening/diagnosis procedure includes assessments of visual acuity, stereo acuity, and presence of amblyopiogenic factors (e.g. strabismus and refractive errors). With no single agreed-upon criterion, one common metric for diagnosing amblyopia is the interocular difference in visual acuity, after exclusion of potential organic defects, refractive error, and strabismus. Recent studies have proposed other potential metrics for diagnosing amblyopia, including interocular differences in contrast sensitivity and in particular the difference in cutoff spatial frequencies. The Pediatric Vision Scanner (PVS), a portable device based on retinal birefringence scanning, has also been developed to automatically detect strabismus, amblyopia, and other serious eye conditions in children as young as 2 years of age. Studies evaluating candidate screening methods for amblyopia have concluded that although tests may differ in terms of screening sensitivity and specificity, the estimated likelihood of amblyopia occurrence was comparable among the tests, and combining different tests could improve diagnostic accuracy.
Although amblyopia screening can be performed in schools, by pediatricians or eye care specialists, automated photo-screening programs usually require specialized instruments and specific expertise. For example, the most common screening procedure assesses visual acuity differences in the potential amblyopic eye between conditions with and without (naked eye) refractive correction. The procedures mandate good compliance, proper eye alignment and refractive error measurements, and accurate prescription of eyeglasses. The screening process can be expensive and inefficient, and is not always easily accessible. There remains an important need for efficient, easy-to-perform, affordable, and reliable screening methods.